original vs repro 289 hipo main caps

[jk66gt350]

Not that I need any - but just wondering and always wanting to learn from experienced people on this forum, given the significant increase in the cost of original hipo main caps, are the reproductions available for $500 worth considering for anyone needing a set?  I know many just want all original components full stop, but other than that, is there any reason someone should not consider these supposedly exact reproductions?   

[acman63]

The only have 4 of the five main caps,  dont have the rear main supposed to use your old one from a standard 289 or 302

[jk66gt350]

Good point Jim, but assuming you have or can find a good rear main, still sounds like a pretty good deal.  Is that and originality the only considerations for potentially buying and using these? 

[acman63]

The Hipo rear main cap is different than the std cap

[shelbydoug]

It should be pointed out that you just can't bolt on a set of caps either new or from another block without line boring them along with the block. Not all shops have the equipment for that. Also, not all blocks will be capable of that procedure.

[jk66gt350]

Interesting - I knew that line boring would be required for new caps or caps from another block, but have never heard that some blocks may not be capable of that procedure.  What conditions or issues would the block have to have to for that to be the case? 

[shelbydoug]

Interesting - I knew that line boring would be required for new caps or caps from another block, but have never heard that some blocks may not be capable of that procedure.  What conditions or issues would the block have to have to for that to be the case?

Usually the machinist needs to mill the bottom of the cap enough to recenter the boring bar. It would be where the center line of the bore on the block is that would determine how much to mill off them. If the original boring favored the block side of the center line, it may not be possible to mill the caps down enough to recenter it.

These were production blocks and all that mattered at the time was that the original caps were in correct orientation to the block. You would be surprised at how much variation there would be from engine to engine.

You would be much better off finding an original block/cap matching assembly. I don't even know why you would be changing caps other then trying to convert a regular block to a HP block and even so, why? There is no significant advantage to even want to bother with that?

[jk66gt350]

Thanks very much for the detailed reply.  As mentioned in my original post, I have no need for a set of these.  It was just interesting to me that it appeared that you could buy supposedly exact repro hp main caps for a fraction of the price that used ones were going for, yet the original sets of used hp main caps are still in high demand and still escalating in price.  I was just curious as to why - and thanks to you and Jim, I now have some very good answers.  That's what I love about this forum - the knowledge you guys have and are willing to share to educate the rest of us on topics like this. 

[gt350hr]

  The reproduction caps are VERY high quality parts, equal to or better than the originals . Allot of effort went into producing them. They are not simple knock offs of unknown material. I don't know the actual reason behind the rear cap not being made , but I can say it virtually never has a problem. #2 and 4 mains are the highest stressed in a 289/ 302 followed by #1 so replacing the four does the trick as far as helping improve the block's durability.
   "I" feel they are superior than the caps from a block 'Hecho en Mexico" and use the repop first.
     Randy

[OldMil]

How about the caps on a Mexican block, does it have the correct HiPo-like rear cap?  Are these machined to the block as well?

[gt350hr]

   No it does not have the correct cap. Yes they are always "machined to a specific block".  A note to ALL. Of late the "musical cap" game ( cap switching) has become popular. IF you are looking at a non VIN numbered bare block , take a close look at the main bearing bores in the block and caps. IF you see a cross hatch pattern , the block has been "line honed".  While this does NOT automatically say the caps have been added it IS THE MOST COMMON way of doing the swap.  Ford "line bored" the blocks when made and have a "straight line" tooling mark , no angles. People switch caps to improve strength ( good thing) and also ( sadly) to deceive. I felt this is important now that so much emphasis is placed on the "born with" block these days.
    For those who say "it needed it " , or "the machine shop said I had to do it" , 221-351W engines RARELY need any "adjustments" to the factory line bore. I haven't had to do one in my 50 years of building them
   Randy